Electronics technology has proliferated with the advent of inexpensive and high performance integrated circuits, including communication transceivers, microprocessors, and memory. As a result, complex electronic systems, such as personal computers and cellular telephones have become widely held consumer goods.
Integrated circuits are fabricated with multiple processing steps. Integrated circuits are often fabricated with one or more device types, including diodes, capacitors, and different varieties of transistors. These devices often have microscopic features that can only be manufactured with critical processing steps that require careful alignment of equipment used to build the devices. The critical processing steps are expensive because (1) they must be accomplished with costly and sophisticated equipment, and experienced operators, and (2) such steps are not always successful. When a processing step, particularly a critical processing step, is unsuccessful, the integrated circuit may fail. As a result, processing yields are decreased and production costs are increased.
Integrated circuits having two or more different device types require more processing steps, particularly critical processing steps, than integrated circuits having fewer device types. As a result, integrated circuit costs increase and yields decrease. Therefore, a process for fabricating an integrated circuit with multiple device types and having reduced processing steps, particularly critical processing steps, is desirable.
One type of integrated circuit is memory, such as flash memory. Memory typically includes a memory array, address decoder, and control logic. The memory array comprises cells, each of which stores a data bit. Control and address commands are externally communicated to the memory. These commands direct the memory array to externally receive or transmit data respectively into or from a specific cell of the memory array.
The control logic and address devices are conventionally implemented with metal-oxide-semiconductor (MOS) transistors. The cells of the memory array are conventionally implemented with flash cells. MOS transistors and flash cells have distinct structures. Typically, these two devices are fabricated with separate processing steps, including critical processing steps. However, it is desirable to cofabricate MOS transistors and flash cells to diminish the number of processing steps, particularly critical processing steps, used to manufacture flash memory.